Liquid crystal displays have a very important specification, that is, brightness, and a most important factor used to determine brightness is aperture ratio. Simply to say, aperture ratio is a proportion of an effective light-transmissive region through which light can pass. When light is emitted from a backlight, not all the light can pass through a panel, due to for example signal lines used for a source-driver chip and a gate-driver chip of an LCD, thin film transistors (TFTs), and storage capacitors used for storage of voltages. These portions are not fully light-transmissive; in addition, they can not display correct grayscales, because light passing through these portions is not under control of a voltage; therefore, they all should be covered with a black matrix, so as to avoid interference with the proper brightness in other light-transmissive regions. After excluding of the above-mentioned opaque regions, a ratio of the remaining effective light-transmissive regions to the whole area is referred to as aperture ratio.
In a liquid crystal display of the prior art, when light is emitted from a backlight, the light will pass through a polarizer sheet, glass, liquid crystal, color filter, and so on, sequentially. Assuming that the light transmittance of various components is as follows: polarizer sheet, 50% (because it only allows polarized light in a single direction to pass through); glass, 95% (two pieces of glass—the upper and the lower glass—which both are required to calculate); liquid crystal, 95%; aperture ratio, 50% (effective light-transmissive regions only occupy a half area); color filter, 27% (assuming that a material by itself has a light-transmittance of 80%, since the color filter itself is colored, it only allows light wave of that color to pass through; with RGB primary colors as an example, a color filter only allows one of the three colors to pass through, and therefore only one third of the brightness is remained; thus, the light transmittance in total is 80%*33%=27%). In calculating with the light-transmittance parameters described above, only 6% of the light emitted from the backlight will remain; and consequently, in order to obtain sufficient brightness for a liquid crystal display, it is necessary to increase the brightness of the backlight, which will increase displaying costs accordingly.